The present invention relates to a vehicle propulsion system, and more particularly to a split torque gearbox for a miniature gas turbine engine powered hybrid unmanned aerial vehicle (UAV).
There is an increased emphasis on the use of UAVs for performing various activities in both civilian and military situations where the use of manned flight vehicles may not be appropriate. Such missions include surveillance, reconnaissance, target acquisition, target designation, data acquisition, communications relay, decoy, jamming, harassment, ordinance delivery, and supply.
One or more piston engines typically power UAV aircraft. Recently, miniature gas turbine engines are becoming more commonplace due to their high-power output, fuel flexibility and lesser noise signature. Disadvantageously, miniature gas turbine engines require relatively complicated gearbox assemblies to step down the speed of the high speed gas turbine engine rotor shaft to effectively power the lower speed flight systems such as rotor and translational propulsive systems typical of a hybrid UAV aircraft.
Typically, an input pinion to a conventional gearbox assembly requires a multiple of bearing supports and articulating couplings between the input pinion and gas turbine rotor shaft. These components increase gearbox assembly weight and sensitivity to shaft disbalance that may be substantial in high revolution miniature gas turbine engines. The bearings and couplings also require fine lubrication and alignment to operate which may complicate assembly and maintenance in a field environment.
Accordingly, it is desirable to provide a lightweight and uncomplicated powerplant system which efficiently steps down the output of a high speed gas turbine engine.